362 Appendix 



metabolic state. This tendency of an organism toward 

 the invariability of its own metabolism has become, in 

 the course of its phyletic evolution, an inherent tendency 

 to pass through all the transient physiological states that 

 could re-establish this necessary condition within it, hence, 

 a tendency to perform all movements that have nour- 

 ishment for their object; yet in doing this it has never 

 relinquished its original character. This results directly 

 from the fact that all inclination to procure new food 

 ceases as soon as the internal nutritive system of the 

 animal has attained its normal state. 



Accordingly, the hydra or sea anemone does not react 

 positively to food except when its metabolism is in a 

 state requiring more nutriment, "unless," says Jennings, 

 "metabolism is in such a state as to require more ma- 

 terial"; for instance, when the large sea anemone 

 Stoichactis helianthus is not hungry, a bit of food 

 placed upon its oral disk occasions the same character- 

 istic "rejecting reaction" as if it were any other disturb- 

 ing object. And all other organisms, the higher as well 

 as the lower, behave in exactly the same fashion. 2 



SchifFs experiments of injecting nutritive substances 

 into the veins of dogs are direct evidence, on the other 

 hand, that the fundamental condition of hunger is the ab- 

 sence of histogenetic substances in the blood, for these 

 injections resulted not only in nourishing the animal but 

 also in allaying its hunger. 



Moreover the fact that hunger, especially as long 

 as it is only moderate, assumes in man the form of a 

 special and localized sensation originating in the wall of 

 the stomach and being the sole cause of the activities 



2 H. S. Jennings, Behavior of Lozver Organisms, pp. 202, 205, 

 etc. New York, MacMillan, 1906. 



